Reduced Data Rates for Energy-Efficient Reed-Solomon FEC on Fading Channels

Abstract

In the CDMA2000 1xEV-DO broadcast service, Reed-Solomon (RS) coding is applied at the medium access control (MAC) layer. Long bursts of errors are corrected by an additional block interleaving mechanism, which improves the performance of RS coding by increasing the time diversity. This is achieved by increasing the width of the error control block (ECB) to convert error bursts into sparse patterns. On the assumption that the number of ECBs transmitted over the air channel in a given interval of time remains constant, we propose performance and energy models of RS decoding under varying conditions of Rayleigh fading on the broadcast channel, which allows for varying levels of block interleaving. Evaluation of this model shows that a higher data rate for the MAC payload and more efficient recovery from bursty errors can be achieved by increasing the level of block interleaving, although it increases the energy consumption. We therefore make the ECB as small as we can without incurring significant performance reduction by sacrificing the data rate to an extent that depends on the channel conditions. We suggest a way of choosing an adequate but energy-efficient level of ECB interleaving and, thus, determine the data rate. Our approach is effective for energy-constrained mobile devices running multimedia applications, which benefit from an increase in energy efficiency, and can tolerate a certain level of packet errors and a reduction in data rate.